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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

STMicroelectronics BUT92

Name: BUT92
Brand: STMicroelectronics
SKU: BUT92
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BUT92

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-204AA, TO-3

Datasheet:: BUT92.pdf

Description:: TRANS NPN 250V 50A TO-3

Quantity:: RFQ Add To RFQ list

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Inventory:8,184

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Product details

Overview

BUT92 from STMicroelectronics is a high-efficiency, fast-switching NPN power transistor in TO-3 package, rated for 250 V V_CEO, 35 A I_C, and 0.8 V typical V_CE(sat) at T_case = 25°C. It delivers rectangular safe operating area (SOA), very low saturation voltage, and 125 A/µs di/dt capability - optimized for hard-switched SMPS, UPS inverters, and motor control stages.

For engineers reviewing the BUT92 datasheet, BUT92 pinout, BUT92 application, or BUT92 equivalent, key selection criteria include its 250 W P_tot at T_case ≤ 25°C, 0.7 °C/W R_thj-case, 250 V V_CEO(sus) under inductive load, and verified 1.4 µs storage time - critical for high-reliability 50–100 kHz switching designs.

Technical Context

The BUT92 employs multiepitaxial planar construction to achieve robust secondary breakdown immunity and wide accidental overload margin. Its SOA is rectangular up to 100 µs, enabling reliable operation without snubbers in clamped-inductive switching.

It features fast dynamic performance: 1.4 µs storage time, 0.15 µs fall time, and 0.3 µs crossover time under V_CC = 200 V, I_C = 35 A, with V_BB = −5 V base drive - supporting efficient zero-voltage transition (ZVT) and resonant converter topologies.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	250 V - maximum collector-emitter voltage with open base; defines hard-switching voltage headroom in DC-link applications
I_C (continuous)	35 A - rated DC collector current; supports ≥500 W output stages with forced-air cooling
V_CE(sat)	0.8 V (typ.) @ I_C = 35 A, I_B = 3.5 A - enables <1.5 W conduction loss per device at full load
R_thj-case	0.7 °C/W - allows junction temperature rise of ≤175°C at 250 W dissipation with 25°C case temp
di_C/dt	125 A/µs (min.) - sustains rapid current turn-on without secondary breakdown in high-frequency converters
t_s (storage)	1.4 µs (typ.) - minimizes dead-time requirements in half-bridge configurations
V_CEO(sus)	250 V @ I_C = 0.2 A, L = 25 mH - validated sustaining voltage under realistic inductive switching stress

Pinout & Package

TO-3 (version "S") metal-can package with isolated collector tab; mounting hole centered on collector terminal; base and emitter leads are axial pins.

Pin/Terminal	Circuit Role	Design Meaning
Collector (Tab)	Main current sink / heat path	Electrically isolated metal tab; must be mounted to heatsink with insulating washer and thermal paste
Base (Lead 1)	Control input for minority-carrier injection	Requires ≥3.5 A peak drive for full saturation; negative V_BB (−5 V) recommended for fast turn-off
Emitter (Lead 2)	Current return path / reference node	Low-inductance connection critical for minimizing V_CE overshoot during switching transitions

Key Features

Feature	Design Value
Rectangular Safe Operating Area (SOA)	Guarantees stable operation up to 100 µs at 250 V/35 A - eliminates need for SOA derating curves in design
Very low V_CE(sat)	0.8 V typ. reduces conduction losses by >30% vs. legacy 1.2 V devices at same current density
Wide accidental overload area	Withstands 75 A I_EM (10 ms pulse) and 250 W P_tot - supports surge-tolerant UPS and motor start-up
Fast dynamic switching	1.4 µs t_s, 0.15 µs t_f enable ≤100 kHz hard-switched operation with minimal dead-time penalty
High h_FE at high current	h_FE > 10 @ I_C = 35 A ensures sufficient current gain for direct TTL-compatible base drive

Applications

Uninterruptible Power Supply (UPS)

Switch-Mode Power Supply (SMPS)

Use Scenario: Inverter stage of line-interactive UPS delivering 1–3 kVA output with battery backup.

IC Role / Device Role / Timing Role: Main switching transistor in half-bridge topology; handles 200 V DC bus and 35 A peak load current.

Use Value: Rectangular SOA and 250 V V_CEO(sus) prevent failure during grid dropout-induced overloads.

Use Scenario: Primary-side switch in 600–800 W telecom rectifier with 100 kHz PWM frequency.

IC Role / Device Role / Timing Role: High-current NPN switch in forward converter; driven by transformer-coupled gate driver.

Use Value: 1.4 µs storage time and 125 A/µs di/dt support tight dead-time control and reduce switching losses.

Motor Control (DC Brushed)

Industrial AC Motor Drive (Inverter Stage)

Use Scenario: H-bridge power stage controlling 1–2 HP brushed DC motors in CNC feed drives.

IC Role / Device Role / Timing Role: Low-side switching element handling bidirectional 35 A stall current with PWM at 8–20 kHz.

Use Value: Very low V_CE(sat) limits thermal rise during continuous duty; 0.7 °C/W R_thj-case enables compact heatsinking.

Use Scenario: Auxiliary inverter leg in 3-phase VFD for HVAC compressors (10–15 kW range).

IC Role / Device Role / Timing Role: Snubberless switching device in clamped-inductive configuration driving IGBT gate drivers.

Use Value: Verified 250 V V_CEW without snubber simplifies layout and improves system reliability under fault conditions.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN power transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BU508A	Lower V_CEO (1500 V), higher V_CE(sat) (1.5 V typ.), slower switching (t_s = 3.5 µs)	Better suited for flyback converters with high voltage isolation; not recommended for 200 V SMPS requiring low loss	Select BU508A only when primary requirement is ultra-high V_CEO, not efficiency or speed
2N3055	Lower I_C (15 A), higher V_CE(sat) (1.1 V), no rectangular SOA, R_thj-case = 1.5 °C/W	Legacy replacement in low-frequency linear regulators; unsuitable for >20 kHz switching or high-power UPS	2N3055 is obsolete for modern SMPS; use only for repair or low-speed analog amplification

Compared with BU508A and 2N3055, BUT92 uniquely combines 250 V rating, 35 A current, sub-1 V saturation, and rectangular SOA - making it the only viable choice for high-efficiency, high-reliability 50–100 kHz hard-switched power stages.

Availability

BUT92 is available at Aetrix Electronics and suitable for uninterruptible power supply (UPS), switch-mode power supplies (SMPS), and motor control applications requiring stable component supply, long-term industrial lifecycle support, and traceable sourcing.

Supply support for BUT92 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing silicon solutions for automotive, industrial, and power management markets.

The BUT92 belongs to ST's high-voltage, high-current bipolar power transistor family - engineered specifically for rugged, snubberless switching in industrial-grade power conversion systems.

FAQ

Is BUT92 pin-compatible with BU208A or 2N3055?

No. BUT92 uses TO-3 (version "S") with isolated collector tab and specific lead spacing (E = 19.0–20.0 mm). BU208A uses TO-218, and 2N3055 uses standard TO-3 with non-isolated tab. Mechanical and thermal mounting differ significantly - direct substitution requires PCB and heatsink redesign.

What base drive current is required for full saturation at 35 A collector current?

ST specifies 3.5 A DC base current for V_CE(sat) ≤ 1.25 V at T_case = 25°C. For reliable operation at 100°C case temperature, ≥4.5 A peak base current with −5 V reverse bias (V_BB) is recommended to minimize storage time and ensure fast turn-off.

Can BUT92 operate without a snubber network in inductive switching?

Yes - BUT92 is characterized for snubberless operation up to 250 V V_CEW with 52 A I_CWoff under specified LC/RB2 conditions (LC = 48 µH, RB2 = 0.7 Ω, T_case = 125°C). This is validated per ST's inductive load test methodology, not theoretical estimation.

What is the maximum allowable case temperature for continuous 35 A operation?

At 35 A I_C and 0.8 V V_CE(sat), power dissipation is ~28 W. With R_thj-case = 0.7 °C/W, junction temperature rise is 19.6°C. Since T_j(max) = 200°C, case temperature may reach up to 180.4°C - but derating is required per SOA curves; ST recommends ≤100°C case temperature for sustained 35 A operation.

BUT92 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-204AA, TO-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 50 A

Voltage - Collector Emitter Breakdown (Max):: 250 V

Vce Saturation (Max) @ Ib, Ic:: 1.2V @ 3.5A, 35A

Current - Collector Cutoff (Max):: 200mA

DC Current Gain (hFE) (Min) @ Ic, Vce:: -

Power - Max:: 250 W

Frequency - Transition:: -

Operating Temperature:: 200°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-3

BUT92 FAQ

1.How can I place an order for BUT92 through Aetrix?

Please submit a Request for Quotation (RFQ) for BUT92 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for BUT92 reliable?

The price and inventory of BUT92 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BUT92 is usually 5 days.

3.What payment methods are accepted for BUT92?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BUT92 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BUT92?

BUT92 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BUT92 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for BUT92?

For technical support, including BUT92 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BUT92 requirements.

6.How does Aetrix verify that BUT92 is sourced from the original manufacturer or authorized distributors?

All BUT92 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that BUT92 meets industry standards.

7.What is the process for return or replacement of BUT92?

All BUT92 units undergo pre-shipment inspection (PSI). If there is an issue with BUT92, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The BUT92 part is unused and in its original packaging.

Return procedure for BUT92:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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